How to build a Control Panel Simulation with Javascript inside an HTML web page, using if-else statement and checkboxes

Many parts of my question(s) are already posted, but putting the peices together is a nightmare. such as the if-else solution had no (javascript) beginning or end (/javascript). I must inform everyone I am creating the file from scratch on keyboard on Notepad and writing code directly. Visually I have controls, now I need to program the if-else and manipulate those controls, as if electrically wired with Switches, indicators, etc. with one Master Power Switch (checkbox). What would help, is a very simple example of this with 2 checkboxes (1 master, 1 slave) logically based on javascript within a single HTML page. Must include (html) (head) (script) (java) etc.